Re: ALTER TABLE ... NOREWRITE option

From: Dimitri Fontaine <dimitri(at)2ndQuadrant(dot)fr>
To: Noah Misch <noah(at)leadboat(dot)com>
Cc: Andres Freund <andres(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndQuadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: ALTER TABLE ... NOREWRITE option
Date: 2012-12-03 10:37:17
Message-ID: m2wqwz4e1u.fsf@2ndQuadrant.fr
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Noah Misch <noah(at)leadboat(dot)com> writes:
> Acquiring the lock could still take an unpredictable amount of time.

I think there's a new GUC brewing about setting the lock timeout
separately from the statement timeout, right?

> being said, I share Tom's doubts. The DEBUG1 messages are a sorry excuse for
> a UI, but I'm not seeing a clear improvement in NOREWRITE.

EXPLAIN ALTER TABLE would be the next step I guess. I discovered plenty
of magic tricks when working on the rewriting support for that command,
and I think exposing them in the EXPLAIN output would go a long way
towards reducing some POLA violations.

Ideally the EXPLAIN command would include names of new objects created
by the command, such as constraints and indexes.

>> My first thought is to add more detailed EXPLAIN support for
>> DDL... Although that unfortunately broadens the scope of this a tiny
>> bit.
>
> That would be ideal.

+1

Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

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